Laser pointer

ABSTRACT

A device to be used in combination with a surgical navigation system for defining the position of a straight line determined by an operating surgeon within a three-dimensional coordinate system in an operating theatre, including a body ( 1 ) with a surface ( 2 ) and at least three markers ( 3 ) which emit waves ( 19 ) and the position of which can be determined within a tree-dimensional coordinate system by a position detector belonging to the surgical navigation system. A laser ( 4 ) mounted on said body ( 1 ) emits a laser beam ( 5 ), directed away from the body ( 1 ), which has a geometrical central beam ( 6 ) and a wave length in the visible range. The laser beam ( 5 ) is emitted in a geometrically defined position in relation to the markers ( 3 ) so that the position of the central beam ( 6 ) in relation to the three-dimensional coordinate system can be calculated from the previously measured positions of said markers ( 3 ) by a computer which is also part of the surgical navigation system.

[0001] The invention relates to a device to be used in combination witha surgical navigation system for defining the position of a straightline determined by an operating surgeon within a three-dimensionalcoordinate system in an operating theatre as claimed in theprecharacterising part of claim 1.

[0002] Increasingly, surgical navigation systems or devices known asComputer Assisted Surgery Systems (CAS) are used for the treatment ofbone fractures in surgical operation theatres. With the aid of imagingtechniques, these devices permit the utilisation of minimally invasivesurgical procedures by enabling a position measuring of surgicalinstruments and devices within a three-dimensional coordinate systemwhich is stationary relative to the operating theatre. This enables acomputer-controlled displacement and positioning of devices such asmedical robots or movable X-ray apparatuses, in particular those havingan X-ray source mounted on one end of a three-dimensionally movable,C-shaped bow and an X-ray receiver mounted on the other end thereof (inthe following briefly referred to as C-bow). A motor-driven andcomputer-controlled, movable C-bow of this type is disclosed in theinternational patent application PCT/CH00/00022.

[0003] Surgical navigation systems including a computer and a positiondetector for measuring the position of three-dimensionally movable,surgical instruments and devices are disclosed, for example, in U.S.Pat. No. 5,383,454 BUCHOLZ and in EP 0,359,773 SCHLÖNDORFF. Surgicalnavigation systems of this type are put on the market, for example, bythe company MEDIVISION, Oberdorf, Switzerland, under the trade name“Surgigate”. In addition to a computer provided with a data memory forstoring X-ray photographs or entire computer tomograms (CTs) taken andstored prior to, or during the operation for diagnostic purposes or forplanning the intervention to be carried out, these systems comprise atleast one position detector. Frequently, optoelectronic positiondetectors are used which are capable of measuring the positions ofoptical markers applied to said surgical instruments or devices within athree-dimensional coordinate system in the operating theatre.Optoelectronic position detectors are commercially available, forexample, under the trade name Optotrak 3020 (manufactured by NorthernDigital, Ontario, Canada).

[0004] Usually, LEDs (light emitting diodes) or IREDs (infraredlight-emitting diodes) are used as optical markers, the positions ofwhich within a three-dimensional coordinate system are detectable by thesensor of the position detector, realised for example in the form ofcameras or CCDs (charge-coupled devices).

[0005] Other position detectors may function on the basis of acousticwaves or magnetic fields, instead of electromagnetic waves.

[0006] In order to define an image plane or an image normal to beoccupied by the C-bow, a pointer provided with markers, such as the onedisclosed in U.S. Pat. No. 5,383,454 BUCHOLZ, may be positioned by theoperating surgeon with its tip on the body of a patient while the shaftof the pointer is oriented in a selected direction corresponding to theimage normal of the x-ray photograph to be taken. Pointers of this typeare commercially available, for example, under the trade name OptotrakDigitizing Probes (manufactured by Northern Digital, Ontario, Canada).The positions of the markers fixed to the pointer are measured by theposition detector and, based on these data, the position and orientationof the straight line defined by the longitudinal axis of the pointerwithin the three-dimensional coordinate system of the operating theatreis calculated by the computer. Subsequently, the C-bow may be displacedin a computer-controlled manner so as to occupy a position andprojection the image normal of which corresponds to the longitudinalaxis of the pointer. A disadvantage with the utilisation of suchpointers resides in the fact that they are relatively short, which makesit necessary for the operating surgeon to approach the patient veryclosely when working with the pointer. In addition, the position of theimage normal relative to the patient is not visualised with these knownpointers, so that only inaccurate predictions of the resultingprojection can be made. Due to the presence of the operating surgeon,the patient, and the C-bow, the visibility of the markers fixed on suchsmall-sized pointers may be strongly limited for the navigation systemand the markers may temporarily be even completely invisible.

[0007] The invention is intended to provide a remedy for this. It isaccordingly an object of the invention to create a pointer embodied insuch a way as to permit the operating surgeon to indicate the imagenormal or the projection plane from a greater distance. The greaterspatial distances between the operating surgeon, the patient, and thesurgical devices made possible by the invention permit an undisturbeddetection of the markers by the sensors of the position detector. Thusit is possible, for example, to position a computer-controlled,motor-driven C-bow close to the patient without running the risk of acollision between the operating surgeon and the C-bow.

[0008] According to the invention, this object is achieved by means of adevice to be used in combination with a surgical navigation system whichshows the features of claim 1.

[0009] The inventive device to be used in combination with a surgicalnavigation system serves for defining the position of a straight linedetermined by the operating surgeon and of a plane extending verticallythereto within a three-dimensional coordinate system in an operatingtheatre. It comprises a body provided with at least three markers saidmarkers emitting waves. A laser is integrated into said body in such away that the laser beam, emitted concentrically to a central beam, isdirected away from the body. The wave length of the laser beam is in thevisible range, so that it is possible for the operating surgeon bydirecting the device and the laser beam adequately with respect to apatient to be treated so as to define a straight line in the operatingtheatre which intersects the patient and which corresponds, for example,to the image normal of a position and projection of a C-bow that is tobe adjusted. The laser is fixed within the body in a defined positionrelative to the markers, so that the direction of the central beam isdefined relative to the positions of the markers. The positions of themarkers are measured by a position detector which is part of thesurgical navigation system, so that the position of a straight linewithin a three-dimensional coordinate system in the operating theatremay be determined by means of a computer which is equally part of thesurgical navigation system and the C-bow may be displaced to the desiredposition and projection in a computer-controlled manner.

[0010] In one embodiment, the device according to the inventioncomprises a handle which in the case of a battery-operated laser may beprovided with a cavity for receiving the batteries.

[0011] The wattage of the laser is in a range of between 2 mw and 1 W,preferably between 2 mw and 25 mw.

[0012] The waves emitted by the markers are either electromagnetic oracoustic waves, depending on the type of position detector used. Ifmarkers emitting electromagnetic waves are used, the followingembodiments of the markers are envisageable:

[0013] LEDs (light-emitting diodes);

[0014] IREDs (infrared light-emitting diodes);

[0015] optical reflectors; or

[0016] a fibre-optic light guide charged by a light source.

[0017] If markers emitting acoustic waves are used, the markers areembodied as acoustic emitters.

[0018] In one embodiment of the device according to the invention, thebody is shaped in the form of a prismatic or cylindrical rod providedwith a longitudinal axis. Preferably, the laser is integrated in the rodin such a way that the central beam coincides with the longitudinal axisof the rod and that the emitted laser beam is directed away from one ofthe rod ends. Three markers may be fixed in a non-collinear way to therod or may be arranged on a straight line, preferably on thelongitudinal axis, the three markers being arranged, in the latter case,at distances (A) or (B), respectively, relative to one another, with (A)being unequal to (B), so that it is possible to determine the directionof emission of the laser beam.

[0019] In another embodiment of the device according to the invention,the body is realised in the form of a planar plate, the markers beingpreferably arranged in a non-collinear way and emitting waves directedaway from the surface of the plate. The laser is inserted substantiallyon centre in the plate, so that the laser beam emitted is directed awayfrom the bottom surface of the plate.

[0020] Preferably, the markers are arranged in a plane extendingparallel to the top surface, said plane and said top surface beinglikely to coincide and the laser beam is emitted vertically to saidplane.

[0021] In a further embodiment of the device according to the invention,the laser comprises a system of lenses adapted to the wave length of thelaser beam in order to allow the laser beam to be emitted in ageometrically defined position and direction relative to the positionsof the markers. Instead of the system of lenses, a fibre-opticappliance, a system of optical reflectors or any other suitable beamdeflection system may be used.

[0022] Further advantageous embodiments of the invention will becharacterised in the dependent claims.

[0023] The advantages achieved by the present invention consistessentially in the fact that the device according to the invention makesit possible to define a straight line and a plane extending verticallythereto, relative to a patient in the operating theatre, which serves asa simple visualisation means for the computer-controlled positioning ofa medical apparatus, such as the adjustment of the position andprojection of a C-bow. Due to the reach of the laser beam, the operatingsurgeon may freely move in the operating theatre when indicating thestraight line by means of the inventive device, so that it is possible,for example, to position the C-bow without getting in the way of theoperating surgeon.

[0024] In the following, the invention and improvements of the inventionwill be illustrated in greater detail with reference to the partiallydiagrammatic representations of several embodiments.

[0025] In the drawings:

[0026]FIG. 1 is a perspective view of one embodiment of the deviceaccording to the invention; and

[0027]FIG. 2 is a side view of another embodiment of the deviceaccording to the invention.

[0028]FIG. 1 shows an embodiment of the device according to theinvention having a body 1 which is shaped in the form of a planar,triangular plate with a top surface 11 and a bottom surface 12, and alaser 4 which is arranged on centre relative to the ground plan of theplate and emits the laser beam 5 away from the bottom surface 12 intothe operating theatre. The emitted laser beam 5 has a wave length in thevisible range and a geometrical central axis 6. In order to allow thelaser beam 5 to be emitted in a geometrically defined position anddirection in relation to the markers 3, the laser 4 comprises means 20,preferably realisable in the form of a system of lenses, which arearranged in the area of the bottom surface 12 on the front portion ofthe laser 4. The body 1 is equally provided with three markers 3embodied as LEDs placed each in one of the corners of the ground plan ofthe plate in such a way that the waves 19 embodied in the form ofelectromagnetic waves are emitted away from the top surface 11 into theoperating theatre. A handle 8 is fixed on the side of the plate by meansof which the body 1 is manually freely movable. The handle 8 comprises acavity 10 wherein two batteries 9 serving as a source of energy for thelaser 4 are accommodated. The power supply of the laser 4 is realisedvia a cable 14 which leads from the batteries 9 to the laser 4 and isintegrated into the body 1. It would also be possible to pass the cable14 on the outside of the body 1, either along the bottom surface 12 oralong the top surface 11. The cables 13, which assure the power supplyof the markers 3, are integrated into the body 1 on part of theirlengths. The markers 3, embodied as LEDs, are supplied in a centralisedway by the navigation system. For this purpose, the markers 3 embodiedas LEDs are controlled in pulsed mode by the navigation system. Thetemporal correlation between the control pulses and the lighting up ofthe individual markers 3 enables the positional detection by thenavigation system of the surgical instruments provided with markers 3 inthe operating theatre.

[0029] The embodiment of the inventive device shown in FIG. 2 differsfrom the embodiment shown in FIG. 1 only in so far as the body 1 isshaped in the form of a cylindrical or prismatic rod 15. The rod 15 hasa central axis 16, a front end portion 18, and a rear end portion 17.The laser 4 is integrated into the rod 15 and extends coaxially to thecentral axis 16. The means 20 permitting the laser beam 5 to be emittedin a geometrically defined position and direction relative to themarkers 3, which as in the above example are preferably realised in theform of a system of lenses, are arranged on the front portion of thelaser 4 and extend in the direction of the front end portion 18, so thatthe geometrical central beam 6 of the laser beam 5 coincides with thecentral axis 16. The handle 8 with the cavity 10 for receiving twobatteries 9 assuring the power supply of the laser 4 is arranged on therod 15 at a right angle to the central axis 16. The power supply of thelaser 4 is realised via the cable 14 which is integrated into the rod 15and connects the laser 4 to the batteries 9. Three markers 3, embodied,as in the above example, in the form of LEDs, are arranged on a straightline coinciding with the central axis 16, one marker 3 being arrangedclose to the front end portion 18, another marker 3 close to the rearend portion 17, and the third marker 3 being located in an intermediateposition on the rod 15. The intermediate marker 3 and the marker 3arranged close to the rear end portion 17 are separated by a distance A,whereas the intermediate marker 3 and the marker 3 arranged close to thefront end portion 18 are separated by a distance B. The distances A andB are of unequal length (A<B) so as to make it possible to determine thedirection of emission of the laser beam 5 from the measurement of thepositions of the markers 3 by the navigation system. As in the aboveexample, the cables 13, which assure the power supply of the markers 3,are integrated into the body 1 on part of their lengths and lead awayfrom the handle 8 towards the navigation system.

1. A device to be used in combination with a surgical navigation systemfor defining the position of a straight line determined by an operatingsurgeon within a three-dimensional coordinate system in an operatingtheatre, including A) a body (1) having a surface (2) and at least threemarkers (3) emitting waves (19) the position of which may be determinedwithin the three-dimensional coordinate system by means of a positiondetector which is part of the surgical navigation system, characterisedin that B) the body (1) comprises a laser (4) which emits a laser beam(5), directed away from the body (1), which has a geometrical centralbeam (6) and a wave length in the visible range; and C) the position ofthe central beam (6) relative to the three-dimensional coordinate systemmay be calculated from the measured positions of the markers (3) bymeans of a computer which is also part of the surgical navigationsystem.
 2. A device as claimed in claim 1, characterised in that thelaser (4) comprises means (20) permitting the laser beam (5) to beemitted in a geometrically defined position and direction relative tothe markers (3).
 3. A device as claimed in claim 1 or 2, characterisedin that the body (1) comprises a handle (8).
 4. A device as claimed inany of the claims 1 to 3, characterised in that the laser (4) may beoperated by at least one battery (9).
 5. A device as claimed in claim 4,characterised in that the handle (8) comprises a cavity (10) wherein theat least one battery (9) is insertable.
 6. A device as claimed in any ofthe claims 1 to 5, characterised in that the laser (4) has a wattage ina range of between 2 mw and 1 W, preferably between 2 mw and 25 mw.
 7. Adevice as claimed in any of the claims 1 to 6, characterised in that thewaves (19) are electromagnetic waves.
 8. A device as claimed in claim 7,characterised in that the markers (3) are LEDs (light-emitting diodes).9. A device as claimed in claim 7, characterised in that the markers (3)are IREDs (infrared light-emitting diodes).
 10. A device as claimed inclaim 7, characterised in that the markers (3) are optical reflectors.11. A device as claimed in claim 7, characterised in that the markers(3) are fibre-optic light guides charged by a light source.
 12. A deviceas claimed in any of the claims 1 to 6, characterised in that the waves(19) are acoustic waves.
 13. A device as claimed in claim 12,characterised in that the markers (3) are acoustic emitters.
 14. Adevice as claimed in any of the claims 1 to 13, characterised in thatthe body (1) is a rod (15) having a longitudinal axis (16), a front endportion (18), and a rear end portion (17) and that the laser (4) isintegrated into the rod (15), so that the laser beam (5) is emittedcoaxially to the central axis (16) in such a way that it is directedaway from either one end portion (17; 18).
 15. A device as claimed inany of the claims 1 to 14, characterised in that three markers (3) arearranged on a straight line, two of said markers (3) being separatedfrom each other by a distance (A) and two markers (3) being separated bya distance (B), the distances (A) and (B) being unequal.
 16. A device asclaimed in claim 15, characterised in that said straight line coincideswith the central beam (6).
 17. A device as claimed in any of the claims1 to 13, characterised in that the body (1) is a planar plate with a topsurface (11) and a bottom surface (12), that the markers (3) arearranged in a non-collinear manner and emit waves from the top surface(11), and that the laser (4) is inserted substantially on centre in theplate, the laser beam (5) being emitted in such a way as to be directedaway from the bottom surface (12).
 18. A device as claimed in claim 17,characterised in that the markers (3) are arranged in a plane extendingparallel to the top surface (11) and that the laser beam (5) is emittedvertically to said plane.
 19. A device as claimed in claim 18,characterised in that said plane is formed by the top surface (11). 20.A device as claimed in any of the claims 2 to 19, characterised in thatthe means (20) comprise a system of lenses adapted to the wave length ofthe laser beam (5).
 21. A device as claimed in any of the claims 2 to19, characterised in that the means (20) comprise a fibre-opticappliance permitting the laser beam (5) to be emitted in a geometricallydefined position and direction relative to the markers (3).